Industrial wastewater generated at steel, mining, plating, oil production and refining operation, and microelectronic industries generally contains high concentrations of sulfate and other contaminants. The promulgation of new regulations often limits the amount of sulfate that can be present in wastewater discharged because of the effects on the environment. Furthermore, wastewater that is not discharged into the environment, but that is reused in other applications, must often be treated to reduce high concentrations of sulfate. Elevated concentrations of sulfate promote scaling on wastewater treatment equipment, reduce the quality of drinking water, and affect the environment. For example, high sulfate concentrations in water can cause the water to have a foul taste and can have a laxative effect in humans and animals. As another example, sulfates are a major dissolved component in rain and can be chemically reduced to form sulfides, which are known to corrode many metals.
Some methods for sulfate removal may not be environmentally friendly, require the use of more chemicals, and may be costly and thus not the most efficient. Processes utilizing barium sulfide require the use of carbon dioxide, which attributes to the greenhouse effect, include sulfides that must be stripped to prevent corrosion of metals, and must conform to regulations regarding barium discharge which can be poisonous and explosive. The use of biological methods may provide difficulties in maintaining optimum, stabilized conditions for bacterial viability. They also result in the production of sulfides that are difficult to remove and metabolic waste which contributes to pollution. Thus, the process disclosed herein may be considered more environmentally friendly and efficient by utilizing a method that only requires calcium and calcium salts.